Lightning-arrester



(No Model.)

E. THOMSON.

LIGHTNING ARRESTBR.

No. 468,497. Patented Feb. 9, 1892.

UNITED STATES PATENT OEEICEr ELII'IU THOMSON, OF LYNN, MASSACHUSETTS,ASSIGNOR TO THE THOMSON- HOUSTON ELECTRIC COMPANY, OF CONNECTICUT.

LIGHTNING-ARRESTER.

SPECIFICATION forming part of Letters Patent No. 468,497, dated February9, 1892.

I Application led May 5, 1890. Serial No. 35 0,659. (No model.)

To @ZZ whom. it may concern:

Be it known that I, ELIHU THOMSON, a citizen of the United States,residing at Lynn,in the county of Essex, State of Massachusetts, haveinvented certain new and useful Improvements in Lightning-Arresters, ofwhich the following is a specification.

My present invention relating to lightningarresters ,has for its objectthe production of a cheap and reliable lightning-arrester for theprotection of apparatus used in connection with electric-light andelectric-power systems of distribution or other lines.

It is the object of my invention also to secure a lightning-arresterwhich will protect the apparatus employed upon electric circuits fromsuccessive atmospheric discharges or induced-current discharges withoutnecessitating the manual manipulating of the arrester after anydischarge or a number of discharges, or, in other words, to obtain alightning-arrester which is entirely automatic in its action and onehaving no moving parts.

Myinvention consists in interposing a mass or sheet of conductingparticles between the line to be protected and the ground, theseconducting particles being arranged contiguous to each other, but not inactual contact, so as to form a continuous conductor for any distanceand so that a discharge in passing to earth must leap over very manyinsulatingspaces, the conducting particles beingsupported or held insome suitable insulating material.

Figure l illustrates one form of my present invention. Figs. 2 and 3show modifications.

In Fig. l, G is an electric generator or motor connected to the mains aZ9. CZ is a connection from one of the mains, as a, to thelightning-arrester and to earth ai E. I prefer, whether the system ofdistribution be a multiple-arc system or a series system or acombination of the two, to place two lightningarresters upon the mains ab, one connected to the line (l and another to the line c, bothconnected to earth. The plate or form L of the arrester is made asfollows: The plate may be molded of any good insulating materialsuch asplaster-of-paris-and while it is in a soft and yielding state particlesof conducting material-,such as copper, iron, lacmay be sprinkled overits surface and forced into the plate by pressure, the particles beingleft with exposed portions projecting from the surface of the plate.Each side of the plate may be, if desired, similarly treated. Over theends of the plate thus formed I place caps C C of copper or othermetal,to one of which caps is attached the line d, leading -to the mainb, and to the other the line leading to earth at E. A static chargeexisting upon the main b, tending to reach earth at E, finds an easypath through the arrester, as this charge has a potential suiiicient tomake a spark over the entire length of the plate L between theconducting particles; but t-he normal working current upon the mains a bhas not a potential sufficient to maintain an arc, and cannotconsequently reach earth through the arrester. The lightning-arrester istherefore selective, permitting only the passage of currents of muchhigher potential than those generated for the mains c b.

An extended surface covered with conducting particles arranged in themanner described is not replaceable by a single disruptive space ofequivalent resistance as measured by a galvanometer, because I find inpractice that a static discharge which will leap and divide over quite anumber. of small disrupting spaces arranged in series is not able toovercome a single space equal to the total of the smaller spaces ifadded together. The discharge can leap the small spaces successivelywith ease.

In Fig. 2 the plate I. is shown as made up of irregularly-shaped piecesof sheet metal, which pieces may be held in a suitable insulatingmaterial-such as described above-by their bent edges and arranged overthe surface of the plate so as not to form a continuous metallicconductor across the plate between the line CZ and earth E, but so thatthere exist numerous small disruptive spaces, across which alightning-discharge or a similar highpotential discharge can force itsway, but which is altogether impassable for any current produced by thegenerator G.

In Fig. 3 I have shown the preferred form of a lightning-arresterconstructed according to my present invention. It is simply a cylinderwith caps C C at each end, to which the IOO line e and earth E areconnected, the surface being prepared in the same manner as are theplates L of Figs. l and 2. t

Other modifications will readily suggest themselves to any one familiarwith the subject, and I do not deem it necessary to describe anythingmore than the typical apparatus illustrated in the lign res hereinreferred to, Which sufficiently explain the action.

What I claim, and desire to secure by Letters Patent, is- Y l. Alightning-arrester consisting of a series of conducting particlessupported in a form of plastic insulating material and arranged so as toform 'a succession of small disruptive spaces in the discharge-path.

2. A lightning-arrester consisting of a form of plastic insulatingmaterial having conducting ends and having conducting-pieces molded inthe surface thereof to form a path for the discharge.

3. A lightning-arrester consisting of a form or support of plasticinsulating material having conducting particles molded in its surfaceand arranged contiguous to one another, but not in actual contact, so asto form a succession of small disruptive spaces in the discharge-path,as described.

ELIHU THOMSON.

Witnesses:

J oHN W. GIBBONEY, M. H. LooBY.

